The present invention relates generally to rotating machines, such as pumps and motors, for use in a subterranean well environment, which machines include radial bearings; and more specifically relates to such machines wherein the radial bearings are compliant bearings with fluid dampening.
Many types of downhole rotating machines, such as pumps and motors and related devices, are known for use in subterranean well environments. These rotating machines are subjected to relatively unique conditions in such wells. Not only must the machines be operative under conditions of relatively high temperature and pressure, but also they must operate satisfactorily when exposed to a variety of types of well fluids. Many types of downhole rotating machines, and in particular, many types of downhole pumps and motors, are subjected to downhole well fluids which include not only the fluidic component but also sand or other solids forming an abrasive component. Additionally, due to the hostile and variable environment, downhole rotating machines often produce substantial vibration, which vibration can exert substantial forces and strains on a bearing system.
Attempts to find a bearing system suitable for withstanding the exposure to well fluids, and to withstand the abrasion which results therefrom, has resulted in attempts to use materials such as ceramics as a bearing surface. A disadvantage presented by the use of ceramics as a bearing material, however, is that the ceramic products are typically relatively brittle, and are thus highly prone to breakage in a subsurface environment where vibration and other mechanical impact forces are common. Additionally, ceramics typically have a different coefficient of thermal expansion than that of other materials typically used in downhole machines. This further leads to inadequate performance of these conventional bearing systems. For example, in some downhole applications where conventional bearing systems including ceramic elements have been utilized, exposure to high temperatures has resulted in the alteration of tolerances such that components which were initially "press fit" become loose and rotatable relative to one another, thereby resulting in failure of the bearing system.
Accordingly, the present invention provides a new radial bearing system particularly adapted for use in a downhole rotating machine, which bearing system provides a fluid dampened compliant bearing both to optimize the dampening of mechanical forces within the bearing system and to facilitate the cooperative use of materials with different performance characteristics at temperature. This new bearing system design, therefore, further allows the use of ceramic components, such as a ceramic bearing sleeve, to provide optimal abrasion resistance of the bearing system.